1. Field of the Invention
The present invention relates to a petroleum well and a method of operating the well to provide power and power storage downhole. In one aspect, the present invention relates to a rechargeable downhole power storage system with logic controlled charge and discharge circuits.
2. Description of Related Art
The Related Applications describe methods for providing electrical power to and communications with equipment at depth in oil or gas wells. These methods utilize the production tubing as the supply and the casing as the return for the power and communications transmission circuit, or alternatively, the casing and/or tubing as supply with a formation ground as the transmission circuit. In either case the electrical losses which will be present in the transmission circuit will be highly variable, depending on the specific conditions for a particular well. These losses cannot be neglected in the design of power and communications systems for a well, and in extreme cases the methods used to accommodate the losses may be the major determinants of the design.
When power is supplied using the production tubing as the supply conductor and the casing as the return path, the composition of fluids present in the annulus, and especially the possible presence of saline aqueous components in that composition (i.e., electrically conductive fluid), will provide electrical connectivity between the tubing and the casing. If this connectivity is of high conductance, power will be lost when it shorts between tubing and casing before reaching a downhole device.
When power is supplied using the casing as the conductor and formation ground as the return path, electric current leakage through completion cement or concrete (between the casing and the earthen formation) into the earth formation can provide a loss mechanism. The more conductive the cement and earth formation, the more electrical current loss occurs as the current travels from the surface through the casing to a downhole location (e.g., a reservoir location at great depth).
The successful application of systems and methods of providing power and/or communication downhole at depth therefore will often require that a means be provided to accommodate the power losses experienced when the power losses are significant.
All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes, and indicative of the knowledge of one of ordinary skill in the art.